It is the purpose of this proposal to identify the biological functions of the multiple forms of alpha-mannosidase in Saccharomyces cerevisiae. A number of different alpha-mannosidase assays will be constructed in order to identify all of the alpha-mannosidase enzyme that exists in yeast cells. Assays will be constructed which measure the release of mannose from glycoproteins, glycopeptides, and short mannose containing compounds. It is proposed that each alpha-mannosidase activity has a unique biological function, and as such, it has unique substrates, regulation and subcellular distribution which are both determined by and indicative of its biological function. Therefore, we will characterize the various alpha-mannosidases with respect to: 1) their physical properties, such as molecular weight and electrophoretic mobilities in analytical gel electrophoresis; 2) by their intracellular localization in specific cellular compartments; 3) by their kinetic properties, including both substrate specificity and regulatory properties; and 4) by mutant analysis. Analysis of these data will allow us to identify the biological functions of these enzymes in eukaryotic cells.